Cut Prestressed Concrete DBL-T Joist
Cut Prestressed Concrete DBL-T Joist
(OP)
Hi All,
Is it acceptable to cut an existing precast and prestressed double-T concrete joist?
The roof joists span about 35 feet. and I need to cut about eight (8) feet off on one end. the newly cut end will be supported on new load bearing and reinforced CMU wall.
do you for see a problem cutting a presstressed joist?
Regards,
Is it acceptable to cut an existing precast and prestressed double-T concrete joist?
The roof joists span about 35 feet. and I need to cut about eight (8) feet off on one end. the newly cut end will be supported on new load bearing and reinforced CMU wall.
do you for see a problem cutting a presstressed joist?
Regards,






RE: Cut Prestressed Concrete DBL-T Joist
RE: Cut Prestressed Concrete DBL-T Joist
RE: Cut Prestressed Concrete DBL-T Joist
Are there just uniform loads on the DT, or are there loads which cause a high amount of shear? In some cases, some shear reinforcing is added at each end, so now you may be cutting this off.
Make sure you check with all of the local precasters in town - they sometimes have original shop drawings of the double tees and they may be able to assist you in the analysis of the DT.
RE: Cut Prestressed Concrete DBL-T Joist
in the original design of the dt, the point of maximum applied moment was where the precaster built the dt to have the point of maximum moment capacity.
assuming uniform loads, by removing 8' from one end, you've now moved the point of maximum load 4' off center from the point of maximum moment capacity ESPECIALLY IF THE TENDON WAS DRAPED AT A V SHAPE.
RE: Cut Prestressed Concrete DBL-T Joist
I am asking this question eventhough the answer might be obvious, because i do not have too much knowledge on the general practice of the prestressed beam producing plants. there might be a practical answer if that was not the case...
Regards,
RE: Cut Prestressed Concrete DBL-T Joist
RE: Cut Prestressed Concrete DBL-T Joist
based on your comments, which makes sense, cutting the joist is then very possible with little or no side effects...
Regards,
RE: Cut Prestressed Concrete DBL-T Joist
BA
RE: Cut Prestressed Concrete DBL-T Joist
The final question is:
Is chipping the DT using the following described procedure acceptable?
CHIPPING PROCEDURE:
After securing the DT with shoring, start chipping the DT from its end and progress with chipping gradually toward the mid span of the DT.
Thank you for your reply and considerations.
Has this been done before? My practical experience of prestressed members is limited but my theoretical and fundamental background is very strong.
Thank you again,
RE: Cut Prestressed Concrete DBL-T Joist
However, due to the shorter span, the tendency for long term creep/deflection in the upward direction will be increased as the prestress force will not change.
Mike McCann
MMC Engineering
RE: Cut Prestressed Concrete DBL-T Joist
You should make a few calls to local precasters near the project site to verify.
What does chipping from the end accomplish? It sounds very labor intensive! Why can't it just be sawn after the new support is in place?
RE: Cut Prestressed Concrete DBL-T Joist
Mike McCann
MMC Engineering
RE: Cut Prestressed Concrete DBL-T Joist
BA
RE: Cut Prestressed Concrete DBL-T Joist
If you find that it is OK, jike's advice is good. Just saw it off. You may need to use multiple saw cuts to avoid binding the blade.
RE: Cut Prestressed Concrete DBL-T Joist
Mike McCann
MMC Engineering
RE: Cut Prestressed Concrete DBL-T Joist
Mike McCann
MMC Engineering
RE: Cut Prestressed Concrete DBL-T Joist
Now, assuming it has not exploded upward, cut off the eight feet at one end. Where is the problem?
BA
RE: Cut Prestressed Concrete DBL-T Joist
Mike McCann
MMC Engineering